The present invention pertains to a device for cooling testing tubes by evaporating a liquid during sampling.
Testing tubes are widely used in conjunction with a appropriate pump for measuring gases, vapors, and aerosols in air and industrial gases. Due to the properties of the reagent systems used in the testing tubes, measurements are possible, in general, only at temperatures of up to a maximum of about 40.degree. C. Unpredictable changes in the indication behavior of the testing tubes may occur above this temperature limit because of the evaporation of reagents.
It is possible to investigate gases with temperatures above 40.degree. C. if the gas and/or the testing tube is cooled. The common practice is to place a probe in front of the testing tube and to wrap both the probe and the testing tube with a few layers of plastic foam. The plastic foam is kept moist during the measurement. The probe (and consequently also the gas to be investigated) are cooled due to the extraction of heat of vaporization (K. Leichnitz: Prufrohrchen-Messtechnik [Test Tube Measurement Technology], Ecomed-Verlagsgesellschaft mbH, 1981).
One disadvantage of this process is the uncontrolled cooling effect, which strongly depends on the temperature, the humidity, and the state of movement of the ambient air. In addition, handling of the wet plastic foam is very complicated, and errors made during wrapping and moistening influence the cooling effect.